The present invention relates to a burner for a chemical reactor more particularly for the manufacture of synthetic gas i.e. synthesis gas.
This burner may convey several fluids separately into the reaction zone.
The burner of the present invention may be used more particularly in the method of partial flame oxidation of hydrocarbons, for manufacturing synthetic gas. It may be mentioned that methods of this type are already applied by Texaco, Shell, . . . By synthetic gas is meant here a mixture of H.sub.2, CO, as well as N.sub.2, CO.sub.2, water vapor . . .
The reactor for this use is formed of a burner and a combustion chamber. The device for quenching the gas may also be an integral part of the reactor. After the combustion, a filling, catalyst or other, may also be placed in the reactor.
The burner of the present invention may be supplied by gaseous or liquid fuel or solid fuel in suspension and by a combustion sustaining means or an oxidizer, air, oxygen or enriched air. Steam may be added in variable proportions to the oxidizer or more generally to the fuel. The gases introduced may be preheated to a greater or lesser degree. The preheating increases the yield of the reactor. By way of example, optimum yield is obtained with natural gas, air and steam, for an O.sub.2 /C ratio between 0.60 and 0.65 for pressurized operations. With preheating greater than 500.degree. C., the H.sub.2 O/C ratio has little influence between 0.05 and 3. It is optimum towards 1. The steam reduces the formation of soot.
For special uses, the O.sub.2 /C ratio may go below 0.6 and beyond 0.65 (up to 1 for example).
Modern methods operate at pressures which may reach 80 bars.
Combustion is as a whole adiabatic.
It must provide the theoretic reaction : EQU CxHy+x/2 O.sub.2 .fwdarw.x CO+y/2 H.sub.2
but is always accompanied by the formation of CO.sub.2 and H.sub.2 O in variable proportions. Thus, the adiabatic balance temperatures may be locally exceeded. Thus, with pure oxygen, temperatures may be met locally very much greater than 1500.degree. C.
The burners proposed are in general tubular or more complex. The simplest technology is represented by two concentric tubes. In this case, the tubes have dimensions (several tens of millimeters) very much greater than the flame front thicknesses. It is then indispensable to let an appreciably residence time elapse (about a second and more) in order to reach the thermodynamic balance. The reactor then comprises zones of high heterogeneity with recirculation of combusting gases.
The multiplicity of tubes would provide a better homogeneity but the number of tubes remains limited for industrial applications. In addition, industrial construction from ceramic remains delicate with tubes. The metal tubes receive the impacts of the hot gas recirculation nuclei and their resistance is affected thereby if there is no cooling.